Power-generating system and method of operating the same



J. KEMNAL 1,751,004

POWER GENERATING SYSTEM AND METHOD OF OPERATING THE SAME March 18, 1930.

2 Sheets-Sheet 1 Original Filed May 7, 1923 NVENTOR.

.LM ATTORNEYS.

.March 18, 1930. J MN 7 1,751,004

POWER GENERATING SYSTEM AND METHOD OF OPERATING THE. SAME Original Fild May 7, 1923 2 Sheets-Sheet 2 INVENTOR.

, II N g gm WEWQM ATTORNEYS.

Patented Mar. 18, 1930 UNITED STAT S PATENT. OFFICE JAMES KEMNAL, OF LONDON, ENGLAND, ASSIGNOR TO THE BABCDOK & WILCOX COMPANY, OF BAYONNE, NEW JERSEY, A CORPORATION OF NEW JERSEY POWER-GENERATIN G SYSTEM AND METHOD OF OPERATING THE SAME Application filed May 7, 1928, Serial No. 887,038; Renewed August 1, 1928,

stood from the following description and the annexed drawings, in which Fig. 1 is a side elevation, partly in secti0n,'of a unit of such 10 a system shown more or less diagrammatically, and Fig. 2 is a front elevation, partly in section, of the arrangement shown in Fig. 1.

Like reference characters indicate like parts in the different views.

, In the illustrative embodiment, a multistage steam turbine 10 is connected to a generator 11 and is supplied with steam from a boiler which, in the form illustrated, has water tubes 12 connected to headers 13, 14, the boiler having a cross drum 15 and a chaingrate stoker 16. Within the boiler setting and above the boiler tubes 12 is a superheater 17 and a reheater 18, the superheater and the reheater being enclosed in a chamber 19, baffles 20 and 21 extending across the boiler tubes to form passes for the gases from the combustion chamber, the baffle 20 having as a continuation a movable bafiie 22 suspended from chains 23 by which the vertical position of the baflie 22 may be changed. The reheater 18 has its tubes connected to drums 18', 18 on either side of the setting. When the baflie 22 is in the position shown in the figures, the gases from the combustion chamber flow upward at the right of the baffle 20 over'the boiler tubes, thence over part of the superheater tubes, thence over thelreheater tubes, thence over the remainder of the superheater tubes, andfrom thencedownward and again upward over the boiler tubes, the gases passing between the setting walls and the easing 19 to the upper end of an air heater 24 and out through the outlet 25. It should be noted that the flue gases pass through passages b at the front of the boiler and a above thecasing" 19 to the up er end of the air heater 24, and down the tu es of the air heater torthe outlet 25. The airheater is provided with leafless-24, 24" to cause the air to flow backand forth across the tubes of the air heater 24. Air for combustion flows in through the inlet 26 over the air heater tubes and then laterally through an opening 27 and.

from thence upwardly through a passage 27 to a passage (1 beneath the top of the setting casing and above the casing 19 and the passage c, and thence downward through passages f between the side walls of the setting and the casing, to openings 28,28 beneath the grate.

Steam from the superheater 17 passes through pipes 29 to the high-pressure stage of the turbine 10. After passing through the high-pressure stage, some or all of the steam, according to the position of the valve 30, will pass through the ipes 31 to the reheater 18, and from thence t rough the pipes 32 to the inlet of the next lower stage of the turbine 10, the supply of steam from the reheater being controlled by a valve 33.

Some of the steam from pipe 31 passes through pipe 34 to a feed water heater 38, the supply being controlled by valve 35. A second feed water heater 37 is supplied with steam from between a pair of stages at lower pressure than that in pipe 31 thiiough pipe 36, controlled by valve 36. The feed water enters the heater 37 from pipe 39, and from thence flows through pipe 40 to the heater 38, from which it. passes to the boiler through pipe 41, controlled by valve 42. By having the heaters in tandem and beating them with steam of successively higher temperatures, the feed water is finally heated to any desired temperature. Exhaust steam passes through pipe43 to the usual condenser. r

It has been found that the efficiency of the heat cycle is increased by withdrawing some of the steam as it passes from one stage of the turbine to another and utilizing the heat in the steam thus drawn off to heat the boiler feed water, and I have found that this efiiciency is increased if suflicient steam is abstracted from the turbine to heat the feed water to a relatively high temperature, say, 300 F. When, however, the feed water is heater to this relatively high temperature, the usual economizer is so inefiicient, because of the relatively small difference between the temperature of the flue gases and the tomperature of the water, that there is practically nothing gained from the use of an economizer. On the other hand, the flue gas temperature will be relatively high, because these gases have contacted only with water cooled heating surfaces which are inthe general boilercirculation' and which" are, therefore, themselves of a comparatively high temperature.

To overcome the waste of heat in the flue gases which might be enough to neutralize the advantages obtained from abstracting steam from" the intermediate stages of the turbine to heat the feed Water, I provide the air heater 24 to abstract heat from the flue gases and returnthe same to the cycle by supplying heated air to the fuel for combustion purpflses. By the combination which I I have illustrated, the efiiciency of the system is greatly increased over the usual one, in

which the feed water would be heated only by the exhaust steam to a relatively low temperature and the temperature of the feed water further raised by passing it through an economizer contacted by the flue gases. I have also found that the total efficiency of the system is-increased if the-quantity of steam drawn from the intermediate stages of the turbine is sufficient to raise the temperature ofthe feed water to at least 300 F. by using two interstage feed water heaters in place of a single interstage heater that would raise the temperature to, say, 212 F.

In the arrangement which I have illus-, trated, it is also possible to control the degree of reheating-of the steam in the reheater 18 without materially affecting the degree of superheat of the superheater 17. By raising the baffle 22, it will be seen that some of the" furnace gases will be short-circuited betwee-n the upper end of the baflie 20 and the lower 7 end of the baffle 22 and that by this means,

some of the gases are prevented from passing bpiler setting enters such settings the economic losses are much less than would be the case if cold air were circulating over the setting, and in the case of air leaking into the furnace, the heated air will, where there are combustible elements in the gases, such as carbon monoxide, tend to burn the combustible gases more readily and thoroughly.

It will be understood that the arrangement shown inthe drawings is merely illustrative and that the embodiment thereof may be widely varied.

I claim:

1, In a system for generating power, a I

steam boiler having a superheater, a furnace for the boiler, a steam reheater inthe boiler setting, a multiple-stage.steam" turbine supplied with steam from the'superheater, pipes to conduct steam from between a pair of stages to the reheaterand from'the reheater to an intermediate stage of the turbine, baffling to direct the furnace gases over boiler heating surfaces, the superheater and the reheater and back to the boiler heating surface, and means whereby the proportion of the furnace gases passing over the reheater may be I varied to regulate the degree of reheating,

2. In a system for generating power, a

steam boiler having a superheater, a furnace for the boiler, a steam reheater in the'boiler setting, a multiple-stage steam turbine supplied with steam from the superheater, pipes for conducting steam from between a pair of stages of the steam turbine to the reheater:

and thence to an intermediate stageTo'f the steam turbine, means for heating'the feed water by a portion of the steam taken from between the pair of stages of the steamturbine, and means for regulating the amount of heat imparted to the steam in said reheater.

3. In a system for generating power, a

' steam boiler having a superheater, a furnace for thesboiler, a steam reheater in the boiler setting, a multiple-stage steam turbine sup plied with steam from the superheater, pipes or conducting steam from between a pair of stages of th e steam turbine to the reheater and thence to an intermediate stage of-the steam I turbine, means for heating the feed water by a portion of the steam taken from between the pair of stages of the steam turbine, and means for regulating the amount of, gases flowing over said reheater. f1

4. In\ a system for generating power, :a steam boiler having a superheater, a furnace for the boiler, a steam reheater in the boiler setting, a multiple-stage steam turbine supplied with steam from the superheater, pipes for conductingsteam from betweena pair of stages of the steam turbine to the reheater and thence to an intermediate stage of the steam turbine, means for heating the feed water'by a predetermined proportionate amount of the steam taken from between the pair of stages of the steam turbine, whereby the amount of heat imparted to the feed water varies in ace cordance with theload, and means for'regulating the amount of heat imparted to the steam in said reheater. I 5. The method of generating power in a system comprising a steam boiler and superheater, a furnace, a steam reheater in the boilhigh pressure stage of the turbine, conducting steam from between a pair of stages of the steam turbine to the reheater, utilizing a portion of the last mentioned steam for heating the feed water, and regulating the amount of heat imparted to the steam in said reheater.

6. The method of generating power in a system comprising a steam boiler and superheater, a furnace, a steam reheater in the boilor setting, a multiple stage steam turbine and a: feed water heater, which consists in conducting steam from the superheater to the high pressure stage of the-turbine, conducting steam from between, a pair of stages of the steam turbine to the reheater, utilizing a portion of the last mentioned steam for heating the feed water, and regulating the amount of gases flowing over said reheater.

7. The method of generating power in a system comprising a steam boiler and superheater, a furnace, a steam reheater in the boiler setting, a multiple stage steam turbine and a feed water heater, which consists in conducting steam from the superheater to the high pressure stage of the turbine, conducting steam from between a pair of stages of the steam turbine to the reheater, utilizing a portion of the last mentioned steam for heating the feed water, and regulating the amount of heat imparted to the steam in said reheater in accordance with the load on said turbine.

8. In a system for generating power, a steam boiler having a superheater, a furnace for the boiler, a steam reheater in the boiler setting, a multiple-stage steam turbine supplied with steam from the superheater, pipes for conducting steam from between a pair of stages of the steam turbine to the reheater and thence to an intermediate stage of the steam turbine, means for heating the feed water by a portion of the steam taken from between the pair of stages of the steam turbine, and means for regulating the superheat of the steam leaving said reheater.

JA1\[ES ICEMNAL. 

